1. Field of the Invention
Example embodiments of the present invention relate to a semiconductor device and a method of forming the same. More particularly, example embodiments of the present invention relate to a magnetic random access memory device and a method of forming the same.
2. Description of the Related Art
A magnetic random access memory (MRAM) device may be considered a novel memory device because of its nonvolatile features and high-speed read/write operation capabilities.
In general, a magnetic tunnel junction (MTJ) pattern may be used to store data at a unit cell of an MRAM device. The MTJ pattern may include a stacked lower ferromagnet and upper ferromagnet layers. A magnetization direction of the lower ferromagnet layer may be fixed, but a magnetization direction of the upper ferromagnet layer may be varied by an external magnet filed. Resistance of the MTJ pattern may change depending on the magnetization directions of the lower and upper ferromagnet layers. The MTJ pattern may have lower resistance when the magnetization directions of the lower and upper ferromagnet layers are the same as compared with when the magnetization directions are in opposite directions. By sensing current difference based on variation in the resistance of the MTJ pattern, it may be possible to determine whether the data stored in the unit cell is a logic level “1” or a logic level “0”.
If the upper ferromagnet layer is oxidized, magnetoresistance of the MTJ pattern may be degraded, which may result in the malfunction of the MRAM device. Magnetoresistance may be defined as a percentage (%) ratio of a difference between highest and lowest resistance values of the MTJ pattern to the highest resistance value. If magnetoresistance is low, the resistance difference may be reduced, which may degrade the data storage property of the MRAM device. To reduce or prevent the oxidation of the upper ferromagnet layers, a method of forming a tantalum layer on the upper ferromagnet layer has been disclosed.
However, tantalum may react with the upper ferromagnet layer at high temperatures of above about 280° C., which may degrade properties of the upper ferromagnet. Accordingly, magnetoresistance of the MTJ pattern may be degraded, which may cause failure of the MRAM device. Therefore, it may be necessary to perform MRAM device manufacturing processes at low temperatures, which may degrade the temperature margin of the manufacturing processes.